Method for grinding metallic workpieces containing, in particular, nickel

ABSTRACT

The invention relates to a method for grinding metallic workpieces containing, in particular, nickel, whereby a rotationally driven grinding wheel ( 2 ) is continuously dressed by a rotationally driven dressing wheel ( 3 ) during the grinding of the workpiece ( 1 ) by the continual advance (vfrd) of the dressing wheel. In order to increase the grinding capacity, the invention provides that with a dressing advance velocity of 1 to 2 μm per rotation of the grinding wheel and with a circumferential velocity of the grinding wheel (vs) of at least 45 m/s, the advance (table velocity vt) is set such that the rate of metal removal is at least 90 mm 3 /mms.

[0001] The invention relates to a method for grinding in particular nickel-containing metallic workpieces, in which a grinding wheel, which is driven in rotation, is continuously dressed by a dressing wheel, which is driven in rotation, during the grinding of the workpiece by means of a continuous infeed of the dressing wheel.

[0002] Methods of this type are known in the prior art as CD grinding. The continuous dressing of the grinding wheel means that the grinding wheel always retains its exact shape. However, it has the drawback of a high consumption of the grinding wheel. The grinding capacity, i.e. the material-removal rate, is determined by the table speed. In the prior art, this is set in such a way that the material-removal rate is below 30 mm³/mms. In the prior art, the infeed rate of the dressing wheel is less than 1 μm/revolution, based on the grinding wheel. The grinding-wheel speed of revolution, i.e. the cutting speed, is at most 30 m/s. The rotation of the dressing wheel is approximately 80% of the grinding-wheel rotational speed, running in the same direction as the grinding wheel.

[0003] The invention is based on the object of increasing the grinding capacity.

[0004] The object is achieved by the invention specified in the claims.

[0005] In claim 1 it is provided that the dressing infeed rate is increased drastically to a level which is between 1 and 2 μm/revolution. The grinding-wheel speed of revolution is set to at least 45 m/s. With these parameters, the advance (table speed) can be set in such a way that the material-removal rate is at least 90 mm³/mms. Surprisingly, it has emerged that a considerable increase in the dressing infeed rate and only a relatively moderate increase in the grinding-wheel speed of revolution leads to a disproportionate increase in the material-removal rate. Surprisingly, it has emerged that when the material-removal rate is increased by increasing the table speed, the normal forces acting on the table remain virtually constant and do not rise in the same way. If the grinding wheel is made from a highly porous material which forms an air volume of, for example, 50%, it is possible to improve the results still further. The cutting speed can be increased to 60 m/s. It is then possible to achieve material-removal rates of more than 100 mm³/MMS, even for nickel alloys, which form long chips. At a grinding-wheel speed of revolution of 80 m/s and a dressing infeed rate of 2 μm/revolution, it is possible to achieve material-removal rates of 300 mm³/mms. The increase in the material-removal rate which is achieved by increasing the dressing infeed rate is explained by the fact that the increase in the dressing infeed leads to an increase in the sharpness of the tool. This is also deemed responsible for the almost imperceptible increase in the normal force. Although the method using the sets of parameters according to the invention leads to faster wear to the grinding wheel, the consumption of the grinding wheel is surprisingly compensated for by the increased material-removal rate, so that overall the grinding capacity is increased. The penetration depth of the grinding wheel, which works using its circumferential surface, is preferably 3 mm. The table speed can reach levels of over 1.8 m/min. The abrasion to the grinding wheel caused by the dressing is greater than the abrasion during grinding.

[0006] Exemplary embodiments of the invention are explained with reference to the appended figures, in which:

[0007]FIG. 1 diagrammatically depicts the device for carrying out the method according to the invention, and

[0008]FIG. 2 shows sets of parameters with which optimum grinding results can be achieved.

[0009] The device for grinding the workpiece 1 comprises a grinding wheel 2 which is continuously driven in rotation and is operated at a rotational speed which is such that it acts on the workpiece 1 with a grinding-contact speed vs. The direction of rotation is indicated by the arrow 2′.

[0010] The grinding wheel 2 is continuously dressed by a dressing wheel 3 which runs in the same direction 3′ and can be displaced in the direction of the arrow 3″. The dressing wheel rotates at approximately 80% of the rotational speed of the grinding wheel. For grinding purposes, the circumferential surface of the grinding wheel 2 penetrates a depth ae into the workpiece 1, which is resting on a moveable table 4 which can be displaced in the direction indicated by arrow 4′ at the table speed vt.

[0011] The grinding wheel consists of a porous material. 25% of the volume is formed by abrasive grain, 15% by a binder, while 50% of the volume of the grinding wheel is air. This is a porous grinding wheel. It is particularly suitable for nickel alloys.

[0012] To enable the considerable horizontal forces which occur at relatively high material-removal rates to be absorbed, the grinding wheel may have a specially reinforced hub (not shown). A grinding wheel in accordance with Austrian patent application A 314/2000, to which reference is made in its entirety at this point, is particularly suitable for this purpose.

[0013] The parameters illustrated in FIG. 2 are operating parameters at which the device illustrated in FIG. 1 gives good grinding results. The first set of parameters corresponds to the prior art. The second set of parameters shows how a slight increase in the grinding-contact speed and a drastic increase in the dressing infeed rate vfrd leads to an initially approximately proportional increase in the material-removal rate.

[0014] A further increase in the contact speed vs to 45 m/s, while only involving approximately doubling the grinding-contact speed, leads to a material-removal rate which is more than four times greater than that achieved with the set of parameters used in the prior art.

[0015] At a contact speed of 50 m/s, with a dressing infeed rate of 1.5 μm/revolution it is even possible to achieve a material-removal rate of 150 mm³/mms. If the contact speed is increased to 80 m/s, with a dressing infeed rate of 2 μm/revolution it is even possible to achieve a material-removal rate of 300 mm³/MMS.

[0016] The sets of parameters illustrated in FIG. 2 were determined by carrying out grinding experiments in which the cutting speed vs and the infeed rate vfrd of the dressing wheel were kept constant and the advance (table speed) vt was increased in steps. The value shown in FIG. 2 for the material-removal rate corresponds to the experiment with the highest advance in which a sufficiently good grinding result was still achieved.

[0017] All features of the invention disclosed are (inherently) pertinent to the invention. The disclosure content of the associated/appended priority documents (copy of the prior application) and of A 314/2000 is hereby incorporated in its entirety in the disclosure of the present application, partly with a view to incorporating features of these documents in claims of the present application. 

1. A method for grinding in particular nickel-containing metallic workpieces, in which a grinding wheel (2), which is driven in rotation, is continuously dressed by a dressing wheel (3), which is driven in rotation, during the grinding of the workpiece (1) by means of a continuous infeed (vfrd) of the dressing wheel, characterized in that, at a dressing infeed rate of 1 to 2 μm per revolution of the grinding wheel and a circumferential speed of the grinding wheel (vs) of at least 45 m/s, the advance (table speed vt) is set in such a way that the material-removal rate is at least 90 mm³/mms.
 2. The method according to one or more of the preceding claims or in particular according thereto, characterized by a highly porous grinding wheel, in particular comprising 50% by volume of air.
 3. The method according to one or more of the preceding claims or in particular according thereto, characterized by a grinding-wheel speed of revolution of more than 50 m/s, preferably more than 60 m/s, and an advance which corresponds to a material-removal rate of more than 100 mm³/mms or more than 150 mm³/mms. 